The structure of the mRNA and genes for photopigments is being examined. The cDNAs made from human eyes were cloned into phage lambda gt 11 using EcoR1 linkers and a human cDNA library was established. A human opsin cDNA (1 Kb long) was isolated from the cDNA library by cross-hybridization with a bovine cDNA rpobe, and identified by DNA sequence determination. We previously have obtained four different genomic clones from placenta and spleen libraries by cross-hybridization with a bovine opsin cDNA probe. One of the genomic clones was identified as a human opsin gene by cross-hybridizataion with human opsin cDNA and by restriction enzyme mapping. An X chromosome, Hind III DNA library screening experiment suggested that two of the human genomic clones are on the X chromosome. One of the genes is nearly full-size, the other is about one half of the gene. We do not know whether these genes are pseudogenes or polymorphic alleles. They are being sequenced in order to establish their primary gene structure. Since rhodopsin and color pigments are likely to have related primary structures, it is possible that some of these genes (particularyl X chromosome linked genes) are indeed those coding for human color pigments. This analysis is a first setp toward a molecular analysis of color-blindness at the gene level.